Artificial
skin made out of electronic, pressure-sensitive material and
semiconductor nanowires has been developed by engineers at the
University of California, Berkeley. This sort of finding has the
potential to overcome challenges in robotics like "adapting"
the amount of force needed to hold and maneuver a variety of
objects.

"Humans
generally know how to hold a fragile egg without breaking it,"
said Ali Javey, associate professor of electrical engineering
and computer sciences. "If we ever wanted a robot that could
unload the dishes, for instance, we'd want to make sure it doesn't
break the wine glasses in the process. But we'd also want the robot
to be able to grip a stock pot without dropping it."

Kuniharu
Takei, post-doctoral fellow in electrical engineering and computer
sciences and lead author of the study, along with Javey and their
team of researchers, are calling the artificial skin "e-skin".
It is the first of its kind in that it is made out of inorganic
single crystalline semiconductors.

"The
problem is that organic materials are poor semiconductors, which
means electronic devices made out of them would often require high
voltages to operate the circuitry," said Javey. "Inorganic
materials, such as crystalline silicon, on the other hand, have
excellent electrical properties and can operate on low power. They
are also more chemically stable. But historically, they have been
inflexible and easy to crack. In this regard, works by various
groups, including ours, have recently shown that miniaturized strips
or wires of inorganics can be made highly flexible - ideal for high
performance, mechanically bendable electronics and sensors."

To
create the skin, germanium/silicon nanowires were grown on a
cylindrical drum, and then rolled onto a sticky substrate, which is a
polyimide film. The nanowires are printed onto the substrate as the
drum rolls, and flexible, thin sheets are formed where electrical
materials can be built.

Researchers
also utilized a different method where nanowires were grown on a flat
surface and then undergo a direction-rubbing process in order to
transfer to the polyimide film. Nanowires are printed on an 18-by-19
pixel square matrix where each pixel holds a transistor made of
hundreds of semiconductor
nanowires. For sensing functionality, the transistors are
integrated with pressure-sensitive rubber on top of them.

E-skin
could help researchers figure out the amount of force needed hold and
maneuver a variety of objects, and could also help patients with
prosthetic limbs regain their sense of touch. With e-skin requiring
only 5 volts of power to function and lasting beyond 2,000 bending
cycles, it's a perfect advancement for the field of robotics.

"This
is the first truly macroscale integration of ordered nanowire
materials for a functional system - in this case, an electronic
skin," said Takei. "It's a technique that can be
potentially scaled up. The limit now to the size of the e-skin we
developed is the size of the processing tools we are using."